Norman Booth

Skyrmion lattice structural transition in MnSi

A triangular-to-square lattice transition of topological magnetic particles (skyrmions) was observed in a chiral magnet MnSi. Magnetic skyrmions exhibit particle-like properties owing to the topology of their swirling spin texture, providing opportunities to study crystallization of topological particles. However, they mostly end up with a triangular lattice, and thus, the packing degree of freedom in the skyrmion particles has been overlooked so far. We report a structural transition of the skyrmion lattice in MnSi. By use of small-angle neutron scattering, we explore a metastable skyrmion state spreading over a wide temperature and magnetic field region, after thermal quenching. The quenched skyrmions undergo a triangular-to-square lattice transition with decreasing magnetic field at low temperatures. Our study suggests that various skyrmion lattices can emerge at low temperatures, where the skyrmions exhibit distinct topological nature and high sensitivity to the local magnetic anisotropy arising from the underlying chemical lattice.

Powder sample-positioning system for neutron scattering allowing gas delivery in top-loading cryofurnaces

A system for positioning powder samples in top-loading cryofurnaces during neutron scattering experiments, while facilitating the successive delivery of gas doses at set temperatures to the sample, has been designed and tested. The positioning system is compatible with a Hiden Isochema IMI instrument as a gas-dosing platform, enabling gases to be delivered to the sample through a centrally located and thermally stabilized capillary line and valve. The positioning system separates into an upper and a lower section, with the lower section enabling the sample to be isolated and inserted into a glove box. This work describes the system using example neutron powder diffraction results obtained with this system in closed-cycle cryofurnaces.

QUOKKA, the pinhole small-angle neutron scattering instrument at the OPAL Research Reactor, Australia: design, performance, operation and scientific highlights

QUOKKA is a 40 m pinhole small-angle neutron scattering instrument in routine user operation at the OPAL research reactor at the Australian Nuclear Science and Technology Organisation. Operating with a neutron velocity selector enabling variable wavelength, QUOKKA has an adjustable collimation system providing source–sample distances of up to 20 m. Following the large-area sample position, a two-dimensional 1 m2 position-sensitive detector measures neutrons scattered from the sample over a secondary flight path of up to 20 m. Also offering incident beam polarization and analysis capability as well as lens focusing optics, QUOKKA has been designed as a general purpose SANS instrument to conduct research across a broad range of scientific disciplines, from structural biology to magnetism. As it has recently generated its first 100 publications through serving the needs of the domestic and international user communities, it is timely to detail a description of its as-built design, performance and operation as well as its scientific highlights. Scientific examples presented here reflect the Australian context, as do the industrial applications, many combined with innovative and unique sample environments.

The structural impact of water sorption on device-quality melanin thin films

The melanins are a class of pigmentary bio-macromolecules ubiquitous in the biosphere. They possess an intriguing set of physico-chemical properties and have been shown to exhibit hybrid protonic-electronic electrical conductivity, a feature derived from a process termed chemical self-doping driven by the sorption of water. Although the mechanism underlying the electrical conduction has been established, how the sorbed water interacts with the melanin structure at the physical level has not. Herein we use neutron reflectometry to study changes in the structure of synthetic melanin thin films as a function of H2O and D2O vapour pressure. Water is found to be taken up evenly throughout the films, and by employing the contrast effect, the existence of labile protons through reversible deuterium exchange is demonstrated. Finally, we determine a sorption isotherm to enable quantification of the melanin-water interactions.

Design and implementation of a differential scanning calorimeter for the simultaneous measurement of small angle neutron scattering

For almost 30 years, at synchrotron facilities, it has been possible to perform small-angle x-ray scattering experiments whilst simultaneously measuring differential scanning calorimetry (DSC). However, a range of challenges exist to enable the collection of simultaneous small-angle neutron scattering (SANS) and DSC data associated not only with intrinsic flux limitations but also scattering geometry and thermal control. The development of a DSC (temperature range ca. −150 °C to 500 °C) suitable for SANS is detailed here and its successful use is illustrated with combined measurements on a binary blend of normal alkanes in which one component has been deuterium labelled.

Thermal stability and irreversibility of skyrmion-lattice phases in Cu2OSeO3

Small angle neutron scattering measurements have been performed to study the thermodynamic stability of skyrmion-lattice phases in Cu

Small Punch Test of LC4/SiCp Metal Matrix Composites

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Does Size Matter? - The Effect of Volume on the Compressive Strength of Open Cell Brittle Ceramics

OSeO

Putting pressure on WOMBAT – outcomes and unique capabilities

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Mechanical Property Enhancement for Al Based Metal Matrix Composites

. We found that the two distinct skyrmion-lattice phases [SkX(1) and SkX(2) phases] can be stabilized through different thermal histories; by cooling from the paramagnetic phase under finite magnetic field, the SkX(2) phase is selected. On the other hand, the 30